A thermal control block needs to accurately control the absolute value of its temperature to a target temperature. Conventionally, for measuring the absolute value of the thermal control block temperature, a method is adopted whereby a calibrated temperature measuring probe is used, and, if the measured temperature differs from the target temperature, correction is made so that the measured temperature matches the target temperature. Generally, it is considered that the limit precision of temperature correction using the calibrated temperature measuring probe is ±0.25° C.
A plurality of individually temperature-controllable thermal control blocks may be provided in a system. In this case, too, when the temperature of the temperature control blocks is individually corrected by using the calibrated temperature measuring probe, the temperature control precision of the thermal control blocks after correction is ±0.25° C. Thus, theoretically, the maximum temperature difference between the thermal control blocks is 0.5° C.
Meanwhile, for temperature correction of the thermal control blocks, a method involving a test strip with the use of a liquid crystal of heat discoloration is proposed (see Patent Document 1, for example). According to the method, in principle, a liquid crystal of heat discoloration is mixed in a test strip that is contacted with a fluid sample, and the test strip temperature is calibrated by detecting discoloration of the liquid crystal when the test strip is controlled to a testing temperature.